Turbidity sensor with improved flow path

ABSTRACT

Systems and methods for increasing the accuracy of a turbidity sensor are disclosed. The systems include a turbidity sensor and a flow module with a specialized flow path, with the turbidity sensor engaging with the flow module such that a measurement zone of the turbidity sensor is disposed within a flow path of the flow module and a bypass path of the flow module does not pass through the measurement zone. The methods include flowing a fluid containing bubbles into a system that separates the fluid in the flow module into a first stream of fluid containing relatively more bubbles and a second stream of fluid containing relatively fewer bubbles, the first stream flowing through a bypass path that does not pass through the measurement zone, and the second stream flowing through the measurement zone of the turbidity sensor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/186,302, filed Jun. 17, 2016, which claims priority to U.S.Provisional Patent Application Ser. No. 62/180,834, filed on Jun. 17,2015, the disclosures of which are hereby fully incorporated herein byreference in their entirety.

BACKGROUND

Turbidity refers to the cloudiness or haziness of a fluid caused bylarge quantities of individual particles that are generally invisible tothe naked eye, but which can be measured using various types ofturbidity sensors. Fluids, such as water, can contain suspended solidmatter consisting of particles of many different sizes. While somesuspended material will be large enough and heavy enough to settlerapidly to the bottom of the container if a liquid sample is left tostand (the settable solids), very small particles will settle only veryslowly or not at all if the sample is regularly agitated or theparticles are colloidal. These small, solid particles cause the liquidto appear turbid. Measuring turbidity is a key test of water quality.

Various types of sensors are utilized for turbidity measurement,including those that use an uninterrupted light source or sources andmeasure the amount of transmitted light or scattered light to determinethe turbidity. One issue that occurs with all sensor designs is thepresence of bubbles in the fluid stream that is being measured. Thediffraction of light through the bubbles distorts the reading, therebygiving an inaccurate turbidity measurement. It would therefore bedesirable to provide systems and methods for increasing the accuracy ofa turbidity sensor.

BRIEF DESCRIPTION

The present disclosure relates, in various embodiments, to systems formeasuring the turbidity of a fluid, and methods for increasing theaccuracy of a turbidity sensor by retarding or eliminating bubbles inthe fluid stream from passing through the measurement zone of theturbidity sensor, or by otherwise diverting the bubbles around theturbidity sensor, thereby increasing the accuracy of the measurement ofthe turbidity sensor in the subject fluid. These systems and methods areuseful for more accurately measuring the turbidity of a fluid containingbubbles. By placing the turbidity sensor into a flow module having aspecialized flow path, the bubbles can be retarded or prevented fromflowing into the measurement zone of the turbidity sensor, which therebyincreases the accuracy of the turbidity sensor.

Disclosed herein is a system for measuring the turbidity of a fluid. Thesystem includes a turbidity sensor and a flow module. The turbiditysensor has a light source and a measurement zone, and the flow modulehas a first end, a second end opposite the first end thereof, an inlet,and an outlet. The inlet and the outlet of the flow module define a flowpath therebetween. The first end of the turbidity sensor engages withthe flow module such that the measurement zone of the turbidity sensoris disposed within the flow path of the flow module; and the flow moduleincludes a bypass path that does not pass through the measurement zone.

In particular embodiments of the system, the inlet of the flow module islocated along a first side thereof and the outlet is located along asecond side thereof, the first side located opposite the second side. Inother embodiments, the inlet and the outlet of the flow module arelocated along the second end thereof. The inlet of the flow module maybe located closer to a bottom end of the flow module than the outlet.The inlet of the flow module may be located below the measurement zoneof the turbidity sensor, and the outlet of the flow module may belocated above the measurement zone of the turbidity sensor.

In certain constructions of the system, the turbidity sensor extendsinto the flow module through an opening in the flow module. The openingin the flow module can extend from the first end thereof to the flowpath thereof.

The bypass path can run along an inner sidewall of the flow module thatextends at least partially about the periphery of an outer sidewall ofthe turbidity sensor, such that the bypass path extends around themeasurement zone of the turbidity sensor and does not pass therethrough.

A fluid-tight seal can be disposed at least partially between theturbidity sensor and the flow module.

The turbidity sensor can be an optical turbidity sensor selected fromthe group consisting of a single beam turbidity sensor, a ratio beamturbidity sensor, and a modulated four beam turbidity sensor. Theturbidity sensor can be an optical turbidity sensor selected from thegroup consisting of a surface scatter turbidity sensor and atransmittance turbidity sensor.

In particular embodiments, the system has a plurality of turbiditysensors. Each turbidity sensor is plugged into the first end of a commonflow module (i.e. one flow module with multiple turbidity sensorsextending into the flow module through a plurality of openings in thefirst end of the flow module). The flow module includes a plurality ofcompartments, each compartment having an inlet, an outlet, and anopening through which a turbidity sensor is inserted into thecompartment. The number of compartments can be equal to the number ofturbidity sensors plugged into the flow module.

In certain embodiments, the turbidity sensor further comprises first andsecond prongs extending outwardly from a base thereof and defining themeasurement zone therebetween.

In further accordance with the present disclosure, a method is disclosedfor increasing the accuracy of a turbidity sensor. The method includesflowing a fluid containing bubbles into a system. The system includes aturbidity sensor and a flow module. The turbidity sensor has a lightsource and a measurement zone, and the flow module has a first end, asecond end opposite the first end thereof, an inlet, and an outlet. Theinlet and the outlet of the flow module define a flow path therebetween.The method further includes placing the turbidity sensor in engagementwith the flow module such that the measurement zone of the turbiditysensor is disposed within the flow path of the flow module; separatingthe fluid in the flow module into a first stream of fluid containingrelatively more bubbles and a second stream of fluid containingrelatively fewer bubbles, the first stream flowing through a bypass paththat does not pass through the measurement zone to the outlet, and thesecond stream flowing through the measurement zone of the turbiditysensor; and measuring the turbidity of the second stream as the secondstream flows through the measurement zone of the turbidity sensor.

In some embodiments, the fluid is continuously flowed through thesystem.

In certain embodiments, the step of placing the turbidity sensor inengagement with the flow module includes placing the turbidity sensorinto the flow module through an opening in the flow module. The openingin the flow module can extend from the top end thereof to the flow paththereof.

The fluid can contain cells or cell debris and be processed in a cellbioreactor before being flowed into the system.

These and other non-limiting characteristics are more particularlydescribed below.

BRIEF DESCRIPTION OF THE DRAWINGS

The following is a brief description of the drawings, which arepresented for the purposes of illustrating the exemplary embodimentsdisclosed herein and not for the purposes of limiting the same.

FIG. 1 is a schematic illustration of a single beam turbidity sensor orturbidimeter.

FIG. 2 is a schematic illustration of a ratio beam turbidity sensor orturbidimeter.

FIG. 3 is a schematic illustration of a modulated four beam turbiditysensor or turbidimeter.

FIG. 4 is a schematic illustration of a surface scatter turbidity sensoror turbidimeter.

FIG. 5 is a perspective view of a first exemplary embodiment of aturbidity sensor according to the present disclosure. The turbiditysensor has a measurement zone at the lower end thereof.

FIG. 6 is an enlarged view of the lower end of the first exemplaryturbidity sensor of FIG. 5. The turbidity sensor has first and secondprongs extending outwardly from a base thereof.

FIG. 7 is a magnified view of section D-D of FIG. 6. The turbiditysensor has a light source in the first prong, a first detector in thesecond prong, and a second detector in the base thereof.

FIG. 8 is a perspective view of a first exemplary embodiment of a flowmodule according to the present disclosure. The flow module has anopening extending from a top end thereof to a flow path thereof.

FIG. 9 is a perspective cross-sectional view of a first exemplary systemincluding a turbidity sensor and a flow module according to the presentdisclosure, along line A-A of FIG. 8.

FIG. 10 is another perspective cross-sectional view of the firstexemplary system of FIG. 9, taken along line B-B of FIG. 8. The flowmodule includes an inlet and an outlet defining a flow paththerebetween. The inlet of the flow module is located closer to thebottom end of the flow module than the outlet.

FIG. 11 is a front cross-sectional view of the first exemplary system ofFIG. 9. The turbidity sensor engages with the flow module such that themeasurement zone of the turbidity sensor is disposed within the flowpath of the flow module. The inlet of the flow module is located belowthe measurement zone of the turbidity sensor and the outlet of the flowmodule is located above the measurement zone of the turbidity sensor.

FIG. 12 is another front cross-sectional view of the first exemplarysystem of FIG. 9, illustrating the flow paths of a first fluid streamcontaining bubbles through the system around the measurement zone of theturbidity sensor, and a second fluid stream containing relatively fewerbubbles compared to the first fluid stream, which passes through themeasurement zone of the turbidity sensor.

FIG. 13 is a perspective view of the first exemplary flow module of FIG.8 illustrating the flow path of a fluid stream containing bubblesthrough the flow module.

FIG. 14 is a top view of the first exemplary flow module of FIG. 8illustrating the flow path of a fluid stream relatively free of bubblesthrough the flow module.

FIG. 15 is a perspective view of a second exemplary system according tothe present disclosure. The system includes a flow module having aplurality of openings and a plurality of turbidity sensors engaging withthe flow module, with the turbidity sensors in a horizontalconfiguration.

FIG. 16 is a perspective cross-sectional view of the second exemplarysystem of FIG. 15, along line C-C of FIG. 15.

DETAILED DESCRIPTION

The present disclosure may be understood more readily by reference tothe following detailed description of desired embodiments and theexamples included therein. In the following specification and the claimswhich follow, reference will be made to a number of terms which shall bedefined to have the following meanings.

Although specific terms are used in the following description for thesake of clarity, these terms are intended to refer only to theparticular structure of the embodiments selected for illustration in thedrawings, and are not intended to define or limit the scope of thedisclosure. In the drawings and the following description below, it isto be understood that like numeric designations refer to components oflike function.

The singular forms “a,” “an,” and “the” include plural referents unlessthe context clearly dictates otherwise.

The term “comprising” is used herein as requiring the presence of thenamed component and allowing the presence of other components. The term“comprising” should be construed to include the term “consisting of”,which allows the presence of only the named component, along with anyimpurities that might result from the manufacture of the namedcomponent.

Numerical values should be understood to include numerical values whichare the same when reduced to the same number of significant figures andnumerical values which differ from the stated value by less than theexperimental error of conventional measurement technique of the typedescribed in the present application to determine the value.

All ranges disclosed herein are inclusive of the recited endpoint andindependently combinable (for example, the range of “from 2 grams to 10grams” is inclusive of the endpoints, 2 grams and 10 grams, and all theintermediate values). The endpoints of the ranges and any valuesdisclosed herein are not limited to the precise range or value; they aresufficiently imprecise to include values approximating these rangesand/or values.

The modifier “about” used in connection with a quantity is inclusive ofthe stated value and has the meaning dictated by the context. When usedin the context of a range, the modifier “about” should also beconsidered as disclosing the range defined by the absolute values of thetwo endpoints. For example, the range of “from about 2 to about 10” alsodiscloses the range “from 2 to 10.” The term “about” may refer to plusor minus 10% of the indicated number. For example, “about 10%” mayindicate a range of 9% to 11%, and “about 1” may mean from 0.9-1.1.

It should be noted that many of the terms used herein are relativeterms. For example, the terms “upper” and “lower” are relative to eachother in location, i.e. an upper component is located at a higherelevation than a lower component in a given orientation, but these termscan change if the device is flipped. The terms “inlet” and “outlet” arerelative to a fluid flowing through them with respect to a givenstructure, e.g. a fluid flows through the inlet into the structure andflows through the outlet out of the structure. The terms “upstream” and“downstream” are relative to the direction in which a fluid flowsthrough various components, i.e. the flow fluids through an upstreamcomponent prior to flowing through the downstream component. It shouldbe noted that in a loop, a first component can be described as beingboth upstream of and downstream of a second component.

The terms “horizontal” and “vertical” are used to indicate directionrelative to an absolute reference, i.e. ground level. However, theseterms should not be construed to require structures to be absolutelyparallel or absolutely perpendicular to each other. For example, a firstvertical structure and a second vertical structure are not necessarilyparallel to each other. The terms “top” and “bottom” or “base” are usedto refer to surfaces where the top is always higher than the bottom/baserelative to an absolute reference, i.e. the surface of the earth. Theterms “upwards” and “downwards” are also relative to an absolutereference; upwards is always against the gravity of the earth.

The term “parallel” should be construed in its lay sense of two surfacesthat maintain a generally constant distance between them, and not in thestrict mathematical sense that such surfaces will never intersect whenextended to infinity.

Currently, the Environmental Protection Agency (EPA) has approved threemethods for the measurement of turbidity, as described in 30 C.F.R. §141.74. Briefly, § 141.74 provides that systems must utilizeturbidimeters that conform to one of several enumerated methods forcompliance purposes. If the instrument does not conform, it may not beused for monitoring under the requirements of the Interim EnhancedSurface Water Treatment Rule (IESWTR).

EPA method 180.1, “Determination of Turbidity by Nephelometry,” is foundin the Agency's publication, Methods for Chemical Analysis of Water andWastes. The method is based upon a comparison of the intensity of lightscattered by a sample under defined conditions, with the intensity oflight scattered by a standard reference suspension. The higher theintensity of scattered light, the higher the turbidity. Readings, inNephelometric Turbidity Units (NTUs), are made in a nephelometerdesigned according to specifications laid out in the EPA method. Aprimary standard suspension is used to calibrate the instrument. Asecondary standard suspension is used as a daily calibration check andis monitored periodically for deterioration using one of the primarystandards. For further information, see Appendix B for EPA Method 180.1.

Standard Method 2130B, found in Standard Methods (1995), is similar toEPA Method 180.1. The 2130B method is also based on a comparison of theintensity of light scattered by the sample under defined conditions,with the intensity of light scattered by a standard reference suspensionunder the same conditions. Again, the higher the intensity of scatteredlight, the higher the turbidity. Formazine polymer is used as theprimary standard reference suspension.

Great Lakes Instruments Method 2 is an instrument-specific, modulatedfour beam method using a ratiometric algorithm to calculate theturbidity value from the four readings that are produced. The comparisonis also based on a comparison of light scattered by the sample underdefined conditions with the intensity of the light scattered by thereference suspension. Once again, the higher the intensity of thescattered light, the higher the turbidity. Readings, in NTUs, are madein a nephelometer designed according to specifications in the method.

Various light-source turbidity sensors employing the above-describedmethods or other methods are known in the art.

A single beam design configuration, such as that shown in FIG. 1, is themost basic turbidimeter design. The single beam design uses only onelight source and one photodetector located at 90° from the incidentlight. The single beam design is the oldest of the modern nephelometersand is typically used with a polychromatic tungsten filament lamp. Thedesign is still in wide use today and yields accurate results forturbidity under 40 NTU, provided that samples have little natural color.In fact, many on-line instruments in use today still utilize the singlebeam design. The single beam design does, however, have limited accuracyat higher turbidities. As turbidity increases and the amount ofscattered light increases, multiple scattering can occur when lightstrikes more than one particle as it reacts with the sample fluid. Theresulting scattered light intensity reaching the 90° detector candiminish as the instrument effectively “goes blind.” For this reason, asingle beam design conforming strictly to EPA Method 180.1 does nottypically demonstrate stable measurement capability at high turbiditiesand is generally only applicable for turbidity readings from 0 to 40NTU. The design of the single beam instrument is also limited by theneed for frequent recalibration of the instrument due to the decay ofthe incandescent light source. Because of the polychromatic nature ofthe light source, these instruments may also demonstrate poorperformance with samples containing natural color. Since most treatedwater samples have low or no color, use of the single beam design can beappropriate for such applications.

The ratio beam turbidimeter design expands upon the single beam concept,but includes additional photodetectors located at other angles than 90°from the incident light. As shown in the exemplary ratio beamturbidimeter design depicted in FIG. 2, the ratio beam design utilizes aforward scatter detector, a transmitted light detector, and for veryhigh turbidity applications, a back scatter detector. The signals fromeach of these detectors are mathematically combined to calculate theturbidity of the sample. A typical ratio mathematical algorithm is asfollows (Standard Methods, 1995):

$T = \frac{I_{90}}{{d_{0}I_{t}} + {d_{1}I_{fs}} + {d_{2}I_{bs}} + {d_{3}I_{90}}}$

where T is the turbidity in NTUs, d₀, d₁, d₂, and d₃ are calibrationcoefficients, I₉₀ is 90° detector current, I_(t) is transmitted detectorcurrent, Ifs is forward scatter detector current, and I_(bs) is backscatter detector current. The use of multiple photodetectors and theratio algorithm gives the instrument much better performance withcolored samples. The transmitted light and the 90° scattered light areaffected almost equally by the color of the sample because they travelnearly the same distance through the sample volume. When the ratio ofthe two readings is taken, the effects of color absorption on the tworeadings tend to cancel mathematically.

Unlike the single beam and ratio beam turbidimeters, a modulated fourbeam instrument design utilizes two light sources and two photodetectors. The two sources and the two detectors are used to implementthe theory of ratio measurements to cancel errors. As shown in theexemplary modulated forum beam ratio sensor depicted in FIG. 3, thelight sources and detectors are located at 90° around the sample volume.This design takes two measurements every 0.5 seconds. In the first phase(left side), light from Light Source #1 is pulsed directly intoPhotodetector #1, while Photodetector #2 simultaneously measures thelight scattered from this pulse at a 90° angle. In the second phase(right side), light from Light Source #2 is pulsed directly intoPhotodetector #2, while Photodetector #1 simultaneously measures thelight scattered from this pulse at a 90° angle. In both phases, thesignal from the photodetector receiving the direct light signal is theactive signal, while the signal from the photodetector measuringscattered light is called the reference signal. In this way, the twophase measurements provide four measurements from two light sources: tworeference signals and two active signals. The turbidity of the sample iscalculated from the four independent measurements taken from the twolight sources using a mathematical algorithm similar to the algorithmused by the ratio instrument design. The result is that errors resultingfrom sample color appear in both the numerator and denominator of themathematical algorithm, and the errors are mathematically canceled. Likethe ratio design, the mathematical algorithm used in the four beamdesign allows for more sensitivity in highly turbid samples and extendsthe range of the instrument to about 100 NTU. The error cancellationachieved by the algorithm also makes the instrument very accurate in the0 to 1 NTU range.

As turbidity increases, light scattering intensifies and multiplescattering can occur as light strikes more than one particle as itinteracts with the fluid. Light absorption by particles can alsosignificantly increase. When particle concentration exceeds a certainpoint, the amount of transmitted and scattered light decreasessignificantly due to multiple scattering and absorption. This point isknown as the optical limit of an instrument. The surface scatter designutilizes a light beam focused on the sample surface at an acute angle.In the exemplary surface scatter design depicted in FIG. 4, lightstrikes particles in the sample and is scattered toward a photodetectorthat is also located above the sample surface. As turbidity increases,the light beam penetrates less of the sample, thus shortening the lightpath and compensating for interference from multiple scattering. Theseinstruments are best suited for measuring high turbidities such as arepresent in raw water and recycle streams. These designs are not,however, currently approved by the EPA.

Instruments utilizing a transmittance design are often referred to asturbidimeters, but these instruments do not measure true turbidity ofwater in NTUs. These instruments are better termed “absorptometers,” asthey measure the amount of light transmitted through a sample ratherthan the amount of light scattered by a sample. Light transmittance ismeasured by introducing a light source to a sample volume and measuringthe relative amount of light transmitted through the sample volume to aphotodetector located opposite the light source. Transmittance valuesare reported as 0 to 100 percent of the incident light sourcetransmitted through the sample. The use of absorptometers in watertreatment has generally been restricted to monitoring spent filterbackwash water to determine relative cleanliness of the filter media.Like surface scatter instruments, these transmittance absorptometers arenot currently approved by the EPA.

In all of the previously described sensor designs, there exists thepotential for bubbles to appear in the fluid stream that is beingmeasured. The existence of bubbles in the sensor area is undesirablebecause diffraction of light through the bubbles causes light scatteringthat is not due to the presence of suspended solids. This distorts thereading, thereby giving a false turbidity measurement.

The present disclosure relates to systems for measuring the turbidity ofa fluid and methods for increasing the accuracy of a turbidity sensor.The systems and methods include a turbidity sensor and a flow modulewith a specialized flow path designed to retard or eliminate bubbles ina fluid from passing through the turbidity sensor, or to minimize theiraccumulation in the measurement zone of the turbidity sensor, or tootherwise divert the bubbles around the turbidity sensor, therebyincreasing the accuracy of the measurement of the turbidity sensor inthe subject fluid.

FIG. 5 shows an exemplary embodiment of a turbidity sensor 100 accordingto the present disclosure. As can be seen in FIG. 5 and FIG. 6, theturbidity sensor generally includes a light source 104 (e.g. an LEDlight source) and a measurement zone 102. The measurement zone 102serves as the area through which the fluid to be measured for turbidityflows. As will be appreciated by those skilled in the art, the turbiditysensor 100 can be any suitable turbidity sensor or turbidimeter, such asthose shown in FIGS. 1-4 and described above. That is, it isspecifically contemplated that the turbidity sensor can be an opticalturbidity sensor, such as a single beam turbidity sensor orturbidimeter, a ratio beam turbidity sensor or turbidimeter, a modulatedfour beam turbidity sensor or turbidimeter, a surface scatter turbiditysensor or turbidimeter, or a transmittance turbidity sensor orturbidimeter. The turbidity sensor 100 generally includes an outersidewall 103 that extends about the periphery of the turbidity sensor100 and defines an outer shell of the turbidity sensor 100.

FIG. 6 and FIG. 7 show enlarged and magnified views of a primary end ofan exemplary turbidity sensor. FIG. 7 is a magnified view of section D-Dof FIG. 6. The exemplary turbidity sensor 100 depicted in FIG. 6includes a first prong 106 and a second prong 108. The first and secondprongs 106, 108 extend outwardly from a primary end of the turbiditysensor 100, the primary end including an end surface 101. As can be bestseen in FIG. 6, the light source 104 is located in the first prong 106.As represented in FIG. 7, as a fluid stream containing particles isflowed through the measurement zone 102 of the turbidity sensor 100,light is emitted from the light source 104 toward a first detector 105.The light reflects off particles in the fluid stream. The reflectedlight can be measured by the first detector 105, 90° scattered light canbe measured by a second detector 107 (e.g., a back or forward scatterdetector), and direct light (i.e., light transmitted at a 0° angle fromthe light source 104) can be measured by a third detector 109 (e.g., atransmitted light detector). In the exemplary turbidity sensor 100 shownin FIG. 7, the first detector 105 and the third detector 109 are locatedin the second prong 108 and the second detector 107 is located in theprimary end of the turbidity sensor 100. In this way, the first andsecond prongs 106, 108 and the end surface 101 define the measurementzone 102 therebetween. Of course this is only one representation of theturbidity sensor.

An exemplary embodiment of a flow module 110 according to the presentdisclosure is shown in FIG. 8, where the flow module has a verticalorientation. Generally speaking, the flow module is a solidstructure/housing that is used to shape different flow paths for thefluid whose turbidity is being measured, and in which the turbiditysensor is located. The flow module 110 has a first end 111, a second end113 opposite the first end, a first side 115, and a second side 117opposite the first side. Here, the first end is a top end, and thesecond end is a bottom end of the flow module. As depicted, the flowmodule 110 is cubic in shape, though it is to be understood that theflow module 110 can be of any suitable shape. A third side 119 isopposite a fourth side 121 of the flow module. The flow module 110further includes an opening 116 in the first end 111 thereof. As will beexplained in greater detail herein, the opening 116 may be of anysuitable size and shape and is generally designed to receive the primaryend of the turbidity sensor 100.

The flow module 110 generally includes an inner sidewall 118 thatdefines the opening 116 in the first end of the flow module. When aturbidity sensor is placed into the opening 116 of the flow module 110in engagement with the flow module 110, the inner sidewall 118 of theflow module 110 generally extends at least partially about the outersidewall 103 of the turbidity sensor 100 (see FIG. 5).

Turning now to FIG. 9, a cross-sectional view of the system 10 is shownin which the turbidity sensor 100 is in engagement with the flow module110. This view is through line A-A of FIG. 8. The turbidity sensor 100extends into the flow module 110 through the first end 111 of the flowmodule 110. More specifically, the turbidity sensor 110 extends into theflow module 110 through the opening in the first end 111 thereof. Asdepicted, the measurement zone 102 of the turbidity sensor 100 iscompletely contained within the flow module 110. Put another way, whenthe turbidity sensor 100 is in engagement with the flow module 110, themeasurement zone 102 of the turbidity sensor 100 is disposed within theflow module 110 between the first end 111 and the second end 113 of theflow module 110. The prongs 106, 108 of of the turbidity sensor arelocated to the sides of the flow path between the inlet 112 and theoutlet 114. Put another way, the fluid flowing through the measurementzone 102 generally flows in a straight line from the inlet 112 to theoutlet 114, and does not have to travel around one of the prongs toenter the measurement zone.

FIG. 10 and FIG. 11 show additional cross-sectional views of the system10 with the turbidity sensor 100 in engagement with the flow module 110,taken along line B-B of FIG. 8. In FIG. 10 and FIG. 11, it can be seenthat the flow module 110 includes an inlet 112 on the first side 115 ofthe flow module 110 and an outlet 114 on the second side 117 of the flowmodule 110. In the exemplary embodiment of the flow module 110 shown inFIG. 10 and FIG. 11, the first side 115 of the flow module 110 islocated opposite the second side 117 thereof. In this regard, the inlet112 is located on an opposite side of the flow module 110 from theoutlet 114. The inlet 112 and the outlet 114 of the flow module 110define a flow path therebetween through which a fluid may flow. Themeasurement zone 102 of the turbidity sensor 100 extends into and isdisposed within the flow path of the flow module 110 when the turbiditysensor 100 is in engagement with the flow module 110. In this regard, itis noted that the opening 116 in the flow module 110 extends from thefirst end 111 of the flow module 110 to the flow path thereof, with theturbidity sensor 100 generally filling the opening 116 between the firstend 111 of the flow module 110 and the flow path. A fluid-tight seal 150(e.g., an O-ring) can be disposed at least partially between theturbidity sensor 100 and the flow module 110, such as between the outersidewall of the turbidity sensor 100 and the inner sidewall of the flowmodule 110 as shown in FIG. 9, or such as between the opening 116 of theflow module 110 and the turbidity sensor 100 as shown in FIG. 11. Thefluid-tight seal generally prevents fluid flowing through the flowmodule 110 from escaping the flow path of the flow module 110.

As can be best seen in the exemplary embodiment of the flow module 110shown in FIG. 11, the inlet 112 is located closer to the second end 113of the flow module 110 than the outlet 114. Put another way the verticaldistance between the inlet and the second end is less than the verticaldistance between the outlet and the second end, or the outlet is higheron the flow module than the inlet. Put yet another way, water flows atan angle upwards through the flow module. Moreover, when the turbiditysensor 100 is in engagement with the flow module 110, such as is shownin FIG. 11, the inlet 112 is located below the measurement zone 102 ofthe turbidity sensor 100, while the outlet 114 is located above themeasurement zone 102 of the turbidity sensor 100.

The interior walls of the flow module 110 are shaped to engage theturbidity sensor and create a flow path through the measurement zone ofthe turbidity sensor. The interior walls also form a bypass path throughwhich fluid can flow around the measurement zone, i.e. the fluid in thebypass path does not pass through the measurement zone. For example, inone embodiment, a fluid containing bubbles is flowed into the flowmodule 110. The fluid can be continuously flowed through the flow module100. Upon being flowed into the flow module 110, the fluid issubsequently separated into a first stream 120 of fluid containingrelatively more bubbles and a second stream 122 of fluid relatively freeof bubbles. The amount of bubbles in the first stream 120 and the secondstream 122 is relative to each other, i.e. the first stream alwayscontains more bubbles than the second stream 122. As shown in FIG. 12,the first stream 120 and the second stream 122 flow together into theflow module 110 via the inlet 112. At this point in time, they can beconsidered a single fluid stream. Due to the presence of the bubbles inthe first stream 120, the first stream 120 flows through the bypass pathof the flow module 110 around the measurement zone 102 of the turbiditysensor 100. As illustrated here, the first fluid stream 120 flows upwardthrough a path that goes around the measurement zone 102. The firststream 120 is then flowed out of the flow module 110 through the outlet114 thereof. In this way, the path of the first stream 120 through theflow module 110 is such that the first stream containing relatively morebubbles does not pass through the measurement zone 102. Another view ofthe flow path of the first stream 120 through the flow module 110 isshown in FIG. 13. Viewing FIG. 12 and FIG. 13, it can be seen how thebypass path follows along an inner sidewall of the flow module 110around the measurement zone 102 of the turbidity sensor 100. In thisway, the specialized flow path retards or eliminates bubbles in thefluid from passing through the measurement zone 102 of the turbiditysensor 100, or otherwise causes the bubbles to flow around themeasurement zone 102 and out the outlet 114 of the flow module 100, notinterfering with the turbidity measurements of the turbidity sensor 110light source. The specialized flow path can be accomplished through acombination of buoyancy and seals that allow the bubbles in the fluidstream to flow outside of the measurement zone 102 of the turbiditysensor 100. As a result of retarding the bubbles from flowing throughthe measurement zone 102 of the turbidity sensor 100, the accuracy ofthe turbidity sensor 100 is thereby improved.

In comparison to the first stream 120, the second stream 122 containingrelatively fewer bubbles flows through the measurement zone 102 of theturbidity sensor 110, as shown in FIG. 12, permitting the turbiditysensor to measure the turbidity of the second stream. Another view ofthe flow path of the second stream 122 through the flow module 110 isshown in FIG. 14. As can be seen in FIG. 12 and FIG. 14, the secondstream 122 flows from the inlet 112 of the flow module 110 to the outlet114 of the flow module 110, with the second stream 122 passing throughthe area into which the measurement zone 102 of the turbidity sensor 100is inserted.

Referring now back to FIGS. 8-11, the interior of the flow moduleincludes a front surface 124 and a rear surface 126 that are located soas to leave a gap 125 between the front surface 124 and the prongs 106of the turbidity sensor. As best seen in FIG. 9, the interior wall isshaped against sides 119, 121 to include another gap 127 between a sidesurface 128 and the prong 106. The gap 127 is spaced away from the innerfloor 129 of the flow path, closer to a top of the flow module, and islocated above the measurement zone 102. The gap 127 is shown here with asomewhat triangular shape, through this particular shape is notsignificant. Referring now to FIG. 12, these gaps 125, 127 form a bypasspath that permits fluid to travel up and around the measurement zone102. Bubbles prefer to rise upwards because they are less dense than thefluid, and so the fluid flowing through the bypass path containsrelatively more bubbles compared to the fluid 122 flowing horizontallythrough the measurement area. This shape also discourage bubbles fromaccumulating within the measurement zone 102.

Turning now to FIG. 15 and FIG. 16, a second exemplary system 20 isshown. System 20 includes several turbidity sensors 100 in engagementwith a flow module 110. Here, the turbidity sensors are in a horizontalorientation instead of a vertical orientation. The plurality ofturbidity sensors 100 can rest on a cradle 140 configured to hold theplurality of turbidity sensors 100 in engagement with the flow module110. Each turbidity sensor 100 extends into the flow module 100 througha corresponding opening (not visible) in the first side 115 of the flowmodule 100. The openings in the flow module 110 of system 20 can besimilar to or the same as opening 116 of flow module 110 of system 10,which was described in detail above. Each opening in the flow module isgenerally configured to receive a single turbidity sensor, such that thenumber of openings in the flow module 110 is equal to the number ofturbidity sensors 100. The flow module 110 of system 20 is divided intoa series of compartments, each compartment having an opening for aturbidity sensor. Each compartment also includes an inlet 112 and anoutlet 114. In flow module 110 of system 20, both the inlet 112 and theoutlet 114 are located on the same side (second side 117) of the flowmodule, rather than on opposite sides as in the flow module of FIG. 8.Each inlet-outlet pair is generally configured to provide fluid ingressand egress to the measurement zone of a single turbidity sensor, suchthat the number of inlets 112 and outlets 114 in the flow module 110 ofsystem 20 is equal to the number of openings in the flow module 110(i.e., equal to the number of turbidity sensors 100 of system 20). Inexemplary system 20 depicted in FIG. 15 and FIG. 16, five turbiditysensors 100 are depicted, though it is to be understood that any desirednumber of turbidity sensors can be placed in engagement with a singleflow module by providing more or less openings, inlets, and outlets inthe flow module. Each outlet 114 is located above the inlet 112, suchthat fluid flow is upwards. It is contemplated that this setup would beused for turbidity measurements of several different fluids. Forexample, this system could be used to measure the turbidity of the fluidin five different bioreactors.

As seen in FIG. 16, in the horizontal orientation, the measurement zone102 is still located between the inlet 112 and outlet 114. Here, abypass path is not present as in the vertical orientation. Rather,although bubbles flow through the measurement zone 102, the bubbles donot accumulate in the measurement zone, and so do not distort thereadings over time.

The systems and methods described herein are useful for increasing theaccuracy of a turbidity sensor. In this regard, one specificallycontemplated area of application for the systems and methods of thepresent disclosure is for determining the reduction in turbidity(measured in NTUs) for a mammalian cell bioreactor and the subsequentfiltration of the cells and cell debris from the bioreactor, leavingbehind the expressed target proteins (monoclonal antibodies andrecombinant proteins) that are the target of the bioreactor process. Oneexample of mammalian cells that may be utilized in this process are CHO(Chinese hamster ovary) cells. The flow rates through these systems canrange from about 0.1 milliliters per minute (mL/min) to about 4 litersper minute (L/min).

The present disclosure has been described with reference to exemplaryembodiments. Obviously, modifications and alterations will occur toothers upon reading and understanding the preceding detaileddescription. It is intended that the present disclosure be construed asincluding all such modifications and alterations insofar as they comewithin the scope of the appended claims or the equivalents thereof.

1. A system for measuring the turbidity of a fluid, the systemcomprising: a turbidity sensor with a body and a first end that includesa light source and a measurement zone between two prongs that extendaway from the body in parallel at the first end; and a flow module thatincludes a top end, a bottom end opposite the top end thereof, an inlet,and an outlet, the inlet and outlet defining a flow path therebetween;wherein the turbidity sensor engages with the flow module such that thetwo prongs of the turbidity sensor are disposed within the flow path ofthe flow module and the outlet is located above the measurement zone;and a gap between an outer sidewall of at least one of the two prongsand an inner wall of the flow module.
 2. The system of claim 1, whereinthe inlet of the flow module is located along a first side thereof andthe outlet is located along a second side thereof, the first sidelocated opposite the second side.
 3. The system of claim 1, wherein boththe inlet and the outlet of the flow module are located along a sameside thereof.
 4. The system of claim 1, wherein the turbidity sensorextends into the flow path through an opening in the flow module.
 5. Thesystem of claim 4, wherein the opening in the flow module extends fromthe top end into the flow path.
 6. The system of claim 4, wherein theopening in the flow module is located on a first side of the flowmodule, and the inlet and the outlet are located on a second side of theflow module opposite the first side of the flow module.
 7. The system ofclaim 1, wherein the inlet of the flow module is located below themeasurement zone of the turbidity sensor.
 8. The system of claim 1,wherein the inlet of the flow module is located closer to the bottom endof the flow module than the outlet thereof.
 9. The system of claim 1,wherein the turbidity sensor is an optical turbidity sensor selectedfrom the group consisting of a single beam turbidity sensor, a ratiobeam turbidity sensor, a modulated four beam turbidity sensor, a surfacescatter turbidity sensor, and a transmittance turbidity sensor.
 10. Thesystem of claim 1, further comprising a plurality of turbidity sensors,each turbidity sensor extending into the flow module through acorresponding opening in the flow module.
 11. The system of claim 1,wherein the gap is configured as a bypass path that does not passthrough the measurement zone.
 12. The system of claim 11, wherein thebypass path runs between an inner wall of the flow module and an outersidewall of the turbidity sensor, above and around the measurement zone.13. A method for increasing the accuracy of a turbidity sensor, themethod comprising: flowing a fluid containing bubbles into a system, thesystem comprising: a turbidity sensor with a body and a first end thatincludes a light source and a measurement zone between two prongs thatextend away from the body in parallel at the first end; and a flowmodule that includes a top end, a bottom end opposite the top endthereof, an inlet, and an outlet, the inlet and outlet defining a flowpath therebetween; placing the turbidity sensor in engagement with theflow module such that the two prongs of the turbidity sensor aredisposed within the flow path of the flow module and the outlet islocated above the measurement zone and to form a gap between an outersidewall of at least one of the two prongs and an inner wall of the flowmodule; and measuring the turbidity of the fluid as the fluid flowsthrough the measurement zone of the turbidity sensor.
 14. The method ofclaim 13, further comprising separating the fluid in the flow moduleinto a first stream of fluid containing relatively more bubbles and asecond stream of fluid containing relatively fewer bubbles, the firststream flowing through the gap configured as a bypass path and does notpass through the measurement zone to the outlet, and the second streamflowing through the measurement zone of the turbidity sensor to bemeasured.
 15. The method of claim 14, wherein the bypass path runsbetween an inner wall of the flow module and an outer sidewall of theturbidity sensor, above and around the measurement zone.
 16. The methodof claim 13, wherein the inlet of the flow module is located along afirst side thereof, and the outlet is located along a second sidethereof, the first side located opposite the second side.
 17. The methodof claim 13 wherein both the inlet and the outlet of the flow module arelocated along a same side thereof.
 18. The method of claim 13, whereinthe inlet of the flow module is located below the measurement zone ofthe turbidity sensor.
 19. A system for measuring the turbidity of afluid, the system comprising: a flow module that includes a top end, abottom end opposite the top end thereof, an inlet, and an outlet, theinlet and outlet defining a flow path therebetween, and an opening inthe top end for receiving a turbidity sensor the opening communicatingwith the flow path; the opening being configured to receive a turbiditysensor with a body and a first end that includes a light source and ameasurement zone between two prongs that extend away from the body inparallel at the first end; wherein the two prongs of the turbiditysensor are disposed within the flow path of the flow module and theoutlet is located above the measurement zone when the turbidity sensoris placed in the opening to engage with the flow module; and a gapbetween an outer sidewall of at least one of the two prongs and an innerwall of the flow module when the turbidity sensor is placed in theopening to engage with the flow module.
 20. The system of claim 19,wherein the inlet of the flow module is located below the measurementzone of the turbidity sensor when the turbidity sensor is placed in theopening to engage with the flow module.